1. Field
Example embodiments relate to output circuits, for example, output circuits capable of controlling swing level of an output data signal, semiconductor devices and communication systems including the same.
2. Description of Related Art
In the related art, semiconductor devices such as volatile and non-volatile memories include input and output blocks. These input and output blocks interface with external devices such as processors and other peripheral devices. A related art output block includes an output driving unit. A related art output driving unit includes an output driving part and an on-die termination part. During an output mode, the output driving part buffers an output data signal, and outputs the buffered output data signal to an external device. The on-die termination part matches impedance with a channel connected between the semiconductor device and the external device to improve signal integrity.
To adapt to various channel environments, it may be necessary to control swing level of the voltage of output data signals from the output driving unit. Conventionally, the swing level of the output data signal is controlled by changing the high power voltage level and low power voltage level of the output driving unit. But, changing the power voltage level has some limitations on controlling the swing level of the output data signal. Particularly, for example, as demand of lower power consumption of semiconductor devices and/or communication systems increases, power may also need to be lowered so that transistors included in the output driving unit may not turn on, and the turn-on resistance of the transistors increases such that operating speed of the semiconductor device or communication system decreases. Also, changing of the power voltage level may cause difficulty in impedance matching so that signal integrity may not be guaranteed.